KernelDistance.cpp

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Written (W) 2010 Christian Widmer
 * Copyright (C) 2010 Max-Planck-Society
 */

#include <shogun/lib/config.h>

#include <shogun/lib/common.h>
#include <shogun/io/SGIO.h>
#include <shogun/distance/KernelDistance.h>
#include <shogun/features/SimpleFeatures.h>

using namespace shogun;

CKernelDistance::CKernelDistance() : CDistance()
{
    init();
}

CKernelDistance::CKernelDistance(float64_t w, CKernel* k)
: CDistance()
{
    init();

    kernel=k;
    width=w;
    ASSERT(kernel);
    SG_REF(kernel);
}

CKernelDistance::CKernelDistance(
    CFeatures *l, CFeatures *r, float64_t w , CKernel* k)
: CDistance()
{
    init();

    kernel=k;
    width=w;
    ASSERT(kernel);
    SG_REF(kernel);

    init(l, r);
}

CKernelDistance::~CKernelDistance()
{
    // important to have the cleanup of CDistance first, it calls get_name which
    // uses the distance
    cleanup();
    SG_UNREF(kernel);
}

bool CKernelDistance::init(CFeatures* l, CFeatures* r)
{
    ASSERT(kernel);
    kernel->init(l,r);
    return CDistance::init(l,r);
}

float64_t CKernelDistance::compute(int32_t idx_a, int32_t idx_b)
{
    float64_t result=kernel->kernel(idx_a, idx_b);
    return exp(-result/width);
}

void CKernelDistance::init()
{
    kernel = NULL;
    width = 0.0;

    m_parameters->add(&width, "width", "Width of RBF Kernel");
    m_parameters->add((CSGObject**) &kernel, "kernel",
                      "Kernel.");
}